For the reduction of Nox from the exhaust gas of diesel engines in particular, a reducing agent, an aqueous urea solution in particular, may be introduced into the exhaust system. In doing so, for example, ammonia is obtained from the urea using a hydrolytic catalyst and the ammonia reacts selectively with the nitrogen oxides contained in the exhaust gas in an SCR catalytic converter to form molecular nitrogen and water (SCR is an abbreviation for “selective catalytic reduction”). A mixing device for mixing the reducing agent with the exhaust gas is referred to in European patent document EP 0 894 523. However, it may exhibit a high flow resistance. The provision of a plate forming a 45 degree angle to the main flow direction of the exhaust gas is referred to in German patent document DE 198 06 265.